A newly-discovered mineral has been found to contain exactly the same elements as the large green crystals that rob the super-hero of his powers.Unlike the fictional rock, the real thing at London's Natural History Museum is white and powdery, emits no radiation, and comes from Serbia rather than outer space.

But scientists who analysed the find were astonished to discover that its chemical composition matched a description of kryptonite in the film Superman Returns.In the 2006 movie, Superman's arch enemy Lex Luthor steals a kryptonite rock fragment from the Metropolis Museum.On the case are written the words "sodium lithium boron silicate hydroxide with fluorine".